The present invention is directed to a removable process unit for use in electrostatographic printing apparatus and in particular to a cover for such a removable process unit having a cavity for the storage of toner cleaned from a photoreceptor.
Recently there has been a tendency in the design of electrostatographic printing apparatus to place one or more of the functional units such as a photoconductor drum or developer housing in a removable processing cartridge or unit so that the customer or operator of the printing machine may replace a functional unit when it's lifetime has been exhausted or a different processing parameter such as toner color is desired. Exemplary of such machines are those described and illustrated, for example, in U.S. Pat. Nos. 3,985,436 to Tanaka et al., 4,556,308 to Hoppner et al. and 5,111,246 to Brailsford et al., all of which are hereby incorporated in their entirety herein by reference. Accordingly, the removable processing cartridges may be designed to contain a photoreceptor, a developing device, a cleaning device as well as a charging device. Alternatively, instead of placing all of the functional elements in a single processing cartridge there may be two or more processing cartridges wherein, for example, the photoreceptor, cleaning device and charge device are in one removable processing cartridge while the developer device is in another removable processing cartridge.
There is a desire, particularly with the smaller electrostatographic printing machines, to make these removable process units or cartridges as small as possible. Accordingly, the capacity of a cleaner sump, for example, in such a removable process unit may be diminished to accommodate this desire for compactness. As a result the capacity to store cleaned toner in such a removable process unit is somewhat limited and is particularly limited where the process unit is being used in an extended life environment wherein it is used until something in it fails rather than being used for only a stated number of prints. As illustrated in FIG. 1, one way of providing additional capacity for the storage of cleaned toner in the past has been to transport cleaned toner from the cleaner sump 10 to the interior of the photoreceptor drum 12. Typically, the transport has been accomplished with the use of a flexible auger 13 within a flexible tube 14 which turns 180 degrees in transporting the toner from the cleaner sump to the interior of the photoreceptor drum. This type of device is difficult to assemble due to the number of parts, their flexible nature and the required side assembly motions. Moreover, it is difficult in many instances to reuse the drum since it is difficult to remove the toner from the interior of the drum without damaging the sensitive photoreceptor surface. Because of the number of parts including a flexible auger and a flexible tube as well as mounting seals and the side assembly the process unit is relatively expensive. In addition, when the drum becomes full of toner the auger continues to rotate and backs out of the drum forcing itself into a twisted knot which may damage the auger and drive mechanism.